An inkjet-type printing device well known in the art prints images by ejecting fine particles of ink in a plurality of colors, such as cyan, magenta, yellow, and black, to form dots on a recording medium.
Ink has a property called permeability that differs according to the type of ink. Permeability indicates the time required for the fine particles of ink to permeate and become fixed to the recording medium. For example, dye-based inks permeate a recording medium more readily than pigment inks. Consequently, when particles of a black pigment ink are ejected onto a sheet of recording medium adjacent to particles of a dye-based color ink, the particles of color ink are first to permeate the medium, and the surface tension between the particles of black ink and the particles of color ink draws the black ink particles toward the color ink particles. Thus, the black ink bleeds into areas that are intended to have dots formed in color ink, potentially resulting in a degraded image quality.
To resolve this problem, a method was proposed to print black using ink in all the plurality of colors excluding black for pixels having a color pixel on the periphery thereof.